1. Field of the Invention
This invention relates to a precision retro-reflective target, tape and, more particularly, to a tape with a transparent backing and precisely sized and positioned retro-reflective targets adhered thereon for use in manufacturing processes and to a method of fabricating such tape.
2. Description of the Background Art
IN the fabrication of products, in particular aircraft components, it is important to validate aligned details and moldlines to insure that the products are properly fabricated to fulfill their intended functions. One technique foe verifying proper fabrication is to use photogrammetry in a manner long emplopyed in the field of surveying and the like. More specifically, it is a common practice to place a tape in adhesive contact onto the side of a fabricated product such as an aircraft part. Such tape is provided with targets in the form of circular dots of a precise size, spaced a precise distance from each other, and precisely located along the length of the tape. In order to insure that such targets are in their proper positions, it is necessary to first record the image of the targets upon a photogrammetric film and then make the proper measurements with the use of a monocomparator. If the sighted targets are in proper position, then the configuration of the fabricated pat to which they are adhered is proper.
In the past, spaced targets have been formed on a retro-reflective tape or sheeting which is inked over or otherwise baked in all areas other than dots to be sighted. Typical of such tape is one marketed by the 3-M Company of Minneapolis, MN under the name of #7610 Scothc.RTM. High Gain Reflective Sheet. It has been found, however, that circular dot targets on sheeting or tape are not always equally sized nor are they always precisely positioned with respect to each other or with respect to the edge of the tape which supports them. Additionally, errors occur in the linear alignment of dot centers, particularly when the tape is aligned on a linear abutment edge of the product workpiece. Consequently the photogrammetric sightings are onto always as accurate as possible, the fault resulting from improperly sized or positioned dots and not the photogrammetric equipment. An additional inaccuracy of prior tapes results from non-transparent support tape functioning as a target backing. The non-transparency causes a "washed-out" effect upon being photographed. Yet another shortcoming of prior tapes is the inability to remove the tape from the part being sighted after use. As a result, the photogrammetric targets often remain on the aircraft and become a part of its structure.
various approaches are disclosed in the patent literature for determining the positioning of one object or part with respect to the other. For example, U.S. Pat. No. 4,492,465 relates to a retro-reflective electro-optical angle measuring system. The particular retro-reflective tape, however, is not shown. In U.S. Pat. No. 4,334,773 to Roper, an adhesive strip is employed with a back light source. This suggests limited utility. The present invention does not require a back light source, is removable from the surface being inspected and is sufficiently flexible to be used on contoured surfaces. In U.S. Pat. No. 3,357,106 to Schneider, a measuring device is disclosed for use in building and excavating. Stick on targets are used but they are not retro-reflected. Unlike the apparatus of Schneider, the present system is designed primarily for use with photogrammetry and other optical equipment. U.S. Pat. No. 3,821,660 to Sheng relates to an apparatus for irradiation of a laser cavity. No retro-reflective tape is utilized. Further, the reflective surface is onto used for inspection of the type that is contemplated herein.
As illustrated by the great number of prior patents and commercial devices and techniques, efforts are continuously being expended in an effort to improve retro-reflective targets and their methods of fabrication. Such efforts are being made to render targets more efficient, reliable, inexpensive and convenient to manufacture and use. None of these previous efforts, however, provides the benefits attendant with the present invention. Additionally , the prior patents and commercial devices and techniques do not suggest the present inventive combination of component elements and method steps arranged and configured as disclosed and claimed herein.
the present invention achieves its intended purposes, objects and advantages through an unobvious combination f component elements and method steps with the use of a minimum number of punched-in parts, at a reasonable cost to manufacture and by employing only readily available materials.
It is therefore an object of the present invention to provide a retro-selective target tape comprising a lower sub-laminate having an upper transparent thick mylar backing bout 2 mils thick, a release sheet therebeneath and a pressure sensitive adhesive therebetween; and an upper sub-laminate having an upper light reflective sheet with a thin, transparent mylar backing about a half mil thick therebeneath and with a pressure sensitive adhesive therebetween and with pressure sensitive adhesive beneath the thin mylar backing, the upper sub-laminate being cut to for ma plurality of circular reflective targets and removed from the lower sub-laminate except for the plurality of circular reflective targets, the pressure sensitive adhesive above the release sheet remaining with the thick mylar backing upon e removal of the adjacent release sheet.
It is a further object of the invention to provide a method of fabricating such tape.
It is a further object of the invention to sight targets properly sized, located and spaced along the length of a transparent tape.
It is a further object of this invention easily remove a photogrammetric tape from the object or pat being sighted.
it is a further object of this invention to improve methods of fabricating tape with target dots properly sized, located and spaced along the length of the tape.
it is a further object of this invention to manufacture aircraft and the products more accurately.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.